Fluid-filled cylindrical vibration-damping device

ABSTRACT

A fluid-filled cylindrical vibration-damping device including a rubber elastic body elastically interconnecting an inner shaft member and an intermediate sleeve, having a first pocket and a second pocket closed by an outer tube member thereby defining a pressure receiving chamber and an equilibrium chamber respectively. Annular sealing portions are provided at axially opposite ends between the intermediate sleeve and the outer tube member. A circumferential groove extends in a circumferential direction between an axial edge of the second pocket and the annular sealing portion in an axial direction, being closed by the outer tube member to provide an orifice passage. One end of the orifice passage circumferentially opens to the pressure receiving chamber while another end circumferentially opens to the equilibrium chamber such that an axial inside dimension of the second pocket is expanded compared to that of an orifice-passage-formation part at a side of opening of the orifice passage.

INCORPORATED BY REFERENCE

The disclosure of Japanese Patent Application No. 2009-044129 filed onFeb. 26, 2009 including the specification, drawings and abstract isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a fluid-filled cylindricalvibration-damping device adapted for use, for example, as an automotiveengine mount.

2. Description of the Related Art

Cylindrical vibration-damping devices have been used as one known classof vibration damping devices for interposition between components thatmake up a vibration transmission system in order to provide vibrationdamped linkage to the components. The cylindrical vibration-dampingdevices have a construction in which an inner shaft fitting adapted tobe attached to one component of the vibration transmission system and anouter tube fitting adapted to be attached to the other component areelastically connected with each other by a main rubber elastic body.

Various fluid-filled cylindrical vibration-damping devices have beenproposed in an effort to mainly improve vibration dampingcharacteristics thereof. Examples of such designs include the devicedisclosed in Japanese Examined Utility Model Publication No.JP-Y-6-25732 which exhibits excellent vibration damping effect utilizingresonance action etc. of non-compressible fluid filled in the interior.More specifically, for example, fluid-filled cylindricalvibration-damping devices include: an inner shaft fitting; an outer tubefitting; a pressure receiving chamber whose wall is partially defined bya main rubber elastic body and an equilibrium chamber whose wall ispartially defined by a diaphragm that are formed diametrically betweentwo fittings; and an orifice passage that connects the pressurereceiving chamber with the equilibrium chamber.

However, fluid-filled cylindrical vibration-damping devices ofconventional construction such as disclosed in JP-Y-6-25732 havedifficulty in providing a sufficient passage length of the orificepassage and tuning the orifice passage to low frequency was thereforedifficult. Specifically, since the orifice passage is formed so as toextend in the circumferential direction between the pressure receivingchamber and the equilibrium chamber, a sufficient passage length of theorifice passage would not be obtained without reducing thecircumferential dimensions of the pressure receiving chamber and theequilibrium chamber. Consequently, vibration damping capabilities willbe diminished due to lack of volume of these chambers.

As one method of ensuring a sufficient passage length of the orificepassage, there has also been proposed a construction which includes aseparate orifice forming member, as disclosed in Japanese UnexaminedPatent Publication No. JP-A-2004-218683. This makes it possible to forman orifice passage with the orifice forming member so as to straddle thepressure receiving chamber and the equilibrium chamber in thecircumferential direction, thereby readily ensuring a passage length ofthe orifice passage. However, the need of the separate member forforming an orifice passage results in problems such as increased numberof manufacturing processes due to the increased number of components, orcomplicated construction of the device.

Meanwhile, U.S. Pat. No. 5,199,691 discloses a construction in which anorifice passage is formed so as to extend in the circumferentialdirection at the locations axially outside of the pressure receivingchamber and the equilibrium chamber. However, this construction posesanother problem that a space for forming an orifice passage will berequired at axially outside of the chambers, causing an increased axialdimension of the fluid-filled cylindrical vibration-damping device. Onthe other hand, if the construction disclosed in U.S. Pat. No. 5,199,691is applied to the device without increasing the axial dimension of thedevice, reducing the axial dimension of each of the pressure receivingchamber and the equilibrium chamber will be necessary. This will cause areduced effective piston surface area of the pressure receiving chamberas well as deterioration of volume compensation action of theequilibrium chamber, making it difficult to exhibit an intendedvibration damping capabilities.

SUMMARY OF THE INVENTION

It is therefore one object of the present invention to provide afluid-filled cylindrical vibration-damping device of novel structure,that is able to effectively exhibit vibration damping effect based onthe flow action of the fluid through the orifice passage and is realizedin a compact design with a smaller number of parts.

The above and/or optional objects of this invention may be attainedaccording to at least one of the following modes of the invention. Thefollowing modes and/or elements employed in each mode of the inventionmay be adopted at any possible optional combinations. It is to beunderstood that the principle of the invention is not limited to thesemodes of the invention and combinations of the technical features, butmay otherwise be recognized based on the teachings of the presentinvention disclosed in the entire specification and drawings or that maybe recognized by those skilled in the art in the light of the presentdisclosure in its entirety.

Specifically, the present invention provides a fluid-filled cylindricalvibration-damping device including: an inner shaft member; a tubularintermediate sleeve disposed outward of the inner shaft member with agap therebetween, and having a first window and at least one secondwindow; a rubber elastic body elastically connecting the inner shaftmember and the intermediate sleeve, the rubber elastic body includes afirst pocket and a second pocket provided at respective circumferentialportions thereof while opening in an outer circumferential surface ofthe intermediate sleeve through the first and second windows of theintermediate sleeve, the rubber elastic body being provided with a slitso that a bottom portion of the second pocket is defined as at least oneflexible film; an outer tube member outwardly fitted onto theintermediate sleeve in order to close an opening of the first pocket anddefine a pressure receiving chamber whose wall is partially defined bythe rubber elastic body and filled with a non-compressible fluid, and inorder to close an opening of the second pocket and define an equilibriumchamber whose wall is partially defined by the flexible film and filledwith the non-compressible fluid; and an orifice passage permitting afluid communication between the pressure receiving chamber and theequilibrium chamber, wherein annular sealing portions are provided ataxially opposite end portions between the intermediate sleeve and theouter tube member over entire circumferences thereof, a circumferentialgroove is provided so as to extend in a circumferential directionbetween at least one of axially opposite edge portions of the secondpocket and the annular sealing portion or portions that are opposed inan axial direction to the at least one of axially opposite edge portionsof the second pocket, the circumferential groove is closed by means ofthe outer tube member to provide the orifice passage, one of oppositeends of the orifice passage opens to the pressure receiving chamber inthe circumferential direction, and another of opposite ends of theorifice passage opens to the equilibrium chamber in the circumferentialdirection such that an axial inside dimension of the second pocket thatdefines the equilibrium chamber is expanded in comparison with that ofan orifice-passage-formation-part at a side of opening of the orificepassage.

With the fluid-filled cylindrical vibration-damping device ofconstruction according to the present invention, since the equilibriumchamber is expanded in the axial direction at the portion which connectswith the orifice passage, wall spring rigidity will become lower,whereby changes in volume can readily arise. With this arrangement, theinitial pressure acting on the equilibrium chamber due to the flowaction of the fluid through the orifice passage will be rapidly absorbedby volume compensation action of the expanded portion. Accordingly, theflow action of the fluid through the orifice passage will effectivelyarise thereby exhibiting an intended vibration damping effect.

Moreover, as the amount of fluid flow through the orifice passageincreases, the entire equilibrium chamber that includes not only theexpanded portion but also the orifice-passage-formation part away fromthe expanded portion will exhibit fluid pressure compensation action onthe pressure receiving chamber. This exhibits excellent vibrationdamping effect.

In addition, in the equilibrium chamber, the orifice passage is formedat least one of the axially opposite edge portions of the section awayfrom the expanded portion. With this arrangement, it is possible toestablish a sufficient passage length of the orifice passage, wherebythe orifice passage will advantageously obtain the degree of freedom intuning and the degree of freedom of design. Furthermore, the orificepassage is formed at the location axially inside of the annular sealingportions, thereby preventing the increased axial dimension of thefluid-filled cylindrical vibration-damping device.

Also, since the opposite end portions of the orifice passage both opento the pressure receiving chamber and the equilibrium chamber in thecircumferential direction, the fluid induced to flow through the orificepassage in the circumferential direction will smoothly flow in and outof the two chambers. This arrangement permits an efficient fluid flowbetween the pressure receiving chamber and the equilibrium chamber,whereby excellent vibration damping capabilities will be attained.

Furthermore, there is no need of the separate member for forming theorifice passage. Therefore, the reduction of the number of componentsand the attachment processes will be realized.

In yet preferred form of the fluid-filled cylindrical vibration-dampingdevice of construction according to the present invention, the secondwindow of the intermediate sleeve has an axial dimension correspondingto that of an expanded portion of the second pocket over an entirecircumferential length thereof, and a part of the second pocket wherethe circumferential groove is defined is integrally formed with therubber elastic body, and projects axially inwardly from the one ofaxially opposite edge portions of the second window.

With the fluid-filled cylindrical vibration-damping device ofconstruction according to the present mode, with respect to theintermediate sleeve it is possible to employ a shape that obviates theneed of specifying top/bottom thereof. Accordingly, while setting theintermediate sleeve with respect to the mold for vulcanization moldingof the rubber elastic body, occurrence of defective products due to anerror in setting orientation of the intermediate sleeve will be avoided.

Moreover, since the orifice-passage-formation part provided at at leastone of the axially opposite edge portions of the second pocket isintegrally formed with the rubber elastic body, the number of componentswill be reduced.

In yet preferred form of the fluid-filled cylindrical vibration-dampingdevice of construction according to the present invention, the secondpocket includes a first bag-shaped portion and a second bag-shapedportion, which are spaced away from each other in the circumferentialdirection, wherein the at least one flexible film comprises a firstflexible film and a second flexible film which partially define thefirst bag-shaped portion and the second bag-shaped portion respectively,wherein a communicating groove is provided for connecting the first andsecond bag-shaped portions, wherein an axially inside dimension of thefirst bag-shaped portion is expanded in comparison with that of thesecond bag-shaped portion at least one of axially opposite sides toprovide the orifice passage between the one of axially opposite edgeportions of the second bag-shaped portion and the annular sealingportion in the axial direction, and wherein the other one of theopposite ends of the orifice passage is connected to the equilibriumchamber at a portion composed of the first bag-shaped portion.

With the fluid-filled cylindrical vibration-damping device ofconstruction according to the present mode, the axially inside dimensionof the first bag-shaped portion is expanded, whereby the firstbag-shaped portion will effectively exhibit volume compensation actionon the pressure receiving chamber. Consequently, the orifice passage isconnected with the first bag-shaped portion, so that the fluid pressureexerted on the equilibrium chamber during the initial fluid flow throughthe orifice passage will be effectively absorbed by the volumecompensation action on the pressure receiving chamber exhibited by thefirst bag-shaped portion.

Furthermore, the second bag-shaped portion is connected with the firstbag-shaped portion, whereby the equilibrium chamber is constructed witha sufficient volume as a whole. Accordingly, even if the amount of fluidflow through the orifice passage increases, the volume compensationaction on the pressure receiving chamber will be effectively exhibitedby the entire equilibrium chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and/or other objects, features and advantages of theinvention will become more apparent from the following description of apreferred embodiment with reference to the accompanying drawings inwhich like reference numerals designate like elements and wherein:

FIG. 1 is an elevational view in axial or vertical cross section of afluid-filled cylindrical vibration-damping device in the form of anautomotive engine mount, which is constructed according to a firstembodiment of the invention, taken along line 1-1 of FIG. 2;

FIG. 2 is a cross sectional view taken along line 2-2 of FIG. 1;

FIG. 3 is a side elevational view of an intermediate sleeve of theengine mount of FIG. 1;

FIG. 4 is a rear elevational view of the intermediate sleeve of FIG. 3;

FIG. 5 is a side elevational view of an integrally vulcanization moldedcomponent of the engine mount of FIG. 1;

FIG. 6 is a rear elevational view of the integrally vulcanization moldedcomponent of FIG. 5;

FIG. 7 is a front elevational view of the integrally vulcanizationmolded component of FIG. 5;

FIG. 8 is a cross sectional view taken along line 8-8 of FIG. 5; and

FIG. 9 is a cross sectional view taken along line 9-9 of FIG. 5.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A more specific understanding of the invention will be provided throughthe following detailed description of the embodiments of the presentinvention, made with reference to the accompanying drawings.

Referring first to FIGS. 1 and 2, there is depicted an automotive enginemount 10 as a first embodiment of the fluid-filled cylindricalvibration-damping device of construction according to the presentinvention. The engine mount 10 has a construction in which an innershaft member 12 of metal and an outer tube member 14 of metal areconnected to one another by a rubber elastic body 16. The inner shaftmember 12 is then mounted onto the power unit side (not shown) while theouter tube member 14 is mounted onto the vehicle body side (not shown)so as to provide vibration damped linkage of the power unit to thevehicle body. In the description hereinbelow, the vertical directionrefers to the vertical direction in FIG. 1 as a general rule, whichcoincides with the axial direction.

To describe in greater detail, the inner shaft member 12 is ahigh-rigidity member made of metal such as iron or aluminum alloy andhas a small-diameter, generally round tube shape that extends straight.A stopper member 18 is attached to the inner shaft member 12. Thestopper member 18 is of generally block shape overall and has a mountinghole 20 that pierces the center section thereof in the axial direction,into which the inner shaft member 12 is inserted. The stopper member 18includes a first stopper portion 22 that projects out towards onediametrical side of the inner shaft member 12 and a second stopperportion 24 that projects out towards the other diametrical side of theinner shaft member 12. The projecting distal end of the first stopperportion 22 has a plate shape that extends in the direction approximatelyorthogonal to the projecting direction, with its surface situated on theprojecting distal end side having a curving surface that corresponds tothe inside peripheral face of the outer tube member 14 described later,thereby ensuring a sufficient abutting surface area against the outertube member 14.

An intermediate sleeve 28 depicted in FIGS. 3 and 4 is disposed outwardof the inner shaft member 12. The intermediate sleeve 28 is formed ofmetal similar to the inner shaft member 12 and has a thin,large-diameter, generally round tube shape. The intermediate sleeve 28includes axially opposite end portions that define a large-diametertubular portion 30 and an axially medial portion that defines asmall-diameter tubular portion 32 so as to provide constricted contoursoverall.

The intermediate sleeve 28 further includes a first window 34 and a pairof second windows 36 a, 36 b. The first and second windows 34 and 36 a,36 b are formed so as to penetrate the intermediate sleeve 28 in thediametrical direction and are circumferentially spaced apart from oneanother with respective prescribed circumferential lengths. In thepresent embodiment, the first window 34 has a length just short ofhalfway around the circumference while the pair of the second windows 36a, 36 b each have a length just short of one-fourth of the circumferenceso as to have an circumferentially inside dimension smaller than that ofthe first window 34. In addition, in the present embodiment, the firstwindow 34 and the second windows 36 a, 36 b each have an axially insidedimension substantially unchanging across the entire length in thecircumferential direction and substantially equal to one another.Moreover, as depicted in FIG. 4, in the intermediate sleeve 28 accordingto the present embodiment, the pair of the second windows 36 a, 36 b aregenerally identical with each other in shape whereby the intermediatesleeve 28 has a symmetrical construction with respect to a plane thatextends in the axially central portion thereof. In other words, theintermediate sleeve 28 will be identical in shape when verticallyinverted.

The inner shaft member 12 and the intermediate sleeve 28 are arranged ina concentric fashion with a diametrical spacing therebetween andconnected with each other by the rubber elastic body 16. The rubberelastic body 16 has a thick-walled, generally round tube shape overalland is arranged with its inside peripheral face bonded by vulcanizationto the outside peripheral face of the inner shaft member 12 while withits outside peripheral face bonded by vulcanization to the insideperipheral face of the intermediate sleeve 28. With this arrangement,the rubber elastic body 16 takes the form of an integrally vulcanizationmolded component 40 incorporating the inner shaft member 12 and theintermediate sleeve 28. In the present embodiment, the intermediatesleeve 28 employs a construction that can be set with respect to themold for vulcanization molding of the rubber elastic body 16 without theneed of specifying top/bottom thereof. Furthermore, in the presentembodiment, the entire surface of the stopper member 18 that is attachedto the inner shaft member 12 is covered by a rubber layer integrallyformed with the rubber elastic body 16.

The rubber elastic body 16 includes a first pocket 42 in the axiallymedial portion thereof. The first pocket 42 has a recessed shape thatopens in the outer circumferential surface of the rubber elastic body 16with a circumferential length just short of halfway around thecircumference. This first pocket 42 further opens in the outercircumferential surface of the intermediate sleeve 28 through the firstwindow 34 formed therein.

Meanwhile, the rubber elastic body 16 includes a first bag-shapedportion 44 and a second bag-shaped portion 46. Like the first pocket 42,the first and second bag-shaped portions 44, 46 are formed in theaxially medial portion of the rubber elastic body 16 and have a recessedshape that opens in the outer circumferential surface thereof. Thecircumferential dimension of each of the first and second bag-shapedportions 44, 46 is just short of one-fourth of the circumference. Thefirst bag-shaped portion 44 opens in the outer circumferential surfaceof the intermediate sleeve 28 through the second window 36 a formedtherein while the second bag-shaped portion 46 opens in the outercircumferential surface of the intermediate sleeve 28 through the secondwindow 36 b formed therein. Moreover, the first and second bag-shapedportions 44, 46 are circumferentially connected with each other via thesection located between the pair of the second windows 36 a, 36 b (acommunicating groove 66 described later) in the small-diameter tubularportion 32 of the intermediate sleeve 28. In this way, a second pocket48 according to the present embodiment is provided including the firstand second bag-shaped portions 44, 46. The first pocket 42 and thesecond pocket 48 are provided with a prescribed separation distance inthe circumferential direction while the first bag-shaped portion 44 andthe second bag-shaped portion 46 are formed being separated from eachother in the circumferential direction.

As depicted in FIG. 2, a slit 50 is provided in the rubber elastic body16 so as to bore in the axial direction between the diametricallyopposed inner shaft member 12 and intermediate sleeve 28. The slit 50 isformed so as to encircle approximately halfway about the outercircumference of the inner shaft member 12 and the two circumferentialends of the slit 50 extend towards diametrically outward in the presentembodiment. The slit 50 is located on the opposite side of the firstwindow 34 of the intermediate sleeve 28 with the inner shaft member 12being interposed therebetween so that the second stopper portion 24 issituated in opposition to the intermediate sleeve 28 with the slit 50being interposed therebetween.

Since the slit 50 is formed in the rubber elastic body 16, the rubberelastic body 16 has thin portions that constitute the bottom portions(inside peripheral walls) of the first and second bag-shaped portions44, 46. By utilizing these thin portions, a first flexible film 52 thatpartially defines the wall of the first bag-shaped portion 44 and asecond flexible film 54 that partially defines the wall of the secondbag-shaped portion 46 are integrally formed with the rubber elastic body16. In the present embodiment, the substantially entire bottom portionof the first bag-shaped portion 44 is defined by the first flexible film52 while the substantially entire bottom portion of the secondbag-shaped portion 46 is defined by the second flexible film 54.

Annular sealing portions 56 are provided on the outer circumferentialsurface of the large-diameter tubular portion 30 of the intermediatesleeve 28. The annular sealing portions 56 are rubber layers that areintegrally formed with the rubber elastic body 16 and as depicted inFIGS. 5 through 7, there are integrally formed seal lips 58 at the outercircumferential surface of the annular sealing portions 56. The seallips 58 are formed with a generally semi-circular shaped cross sectionthat is convex towards the outer circumferential side and extendscontinuously over the entire circumference. In the present embodiment,two seal lips 58 are provided with a prescribed separation distance inthe axial direction at each axial end portion of the intermediate sleeve28.

A passage forming rubber 60 is provided on the outer circumferentialsurface of the small-diameter tubular portion 32 of the intermediatesleeve 28. The passage forming rubber 60 is integrally formed with therubber elastic body 16 and the annular sealing portions 56, and theouter circumferential surface of the passage forming rubber 60 issituated on substantially the same round tube face as the outercircumferential surface of the annular sealing portions 56.

On the outer circumferential face of the passage forming rubber 60, sealribs 62 are integrally formed with the seal lips 58 and project outextending along with a circumferential groove 64 (discussed later) inthe circumferential and/or axial direction. In the present embodiment,both of the annular sealing portions 56 and the passage forming rubber60 are integrally formed with the rubber elastic body 16. The seal lips58 and the seal ribs 62 are also integrally formed therewith.

Here, the passage forming rubber 60 is provided at a portion that doesnot overlap the second window 36 a while partially projecting over oneaxial end of the second window 36 b. Specifically, as depicted in FIGS.5 and 6, the passage forming rubber 60 partially projects from the axialupper side towards the axial lower side of the second window 36 b andextends over the axial upper end of the second window 36 b in thecircumferential direction. In other words, the passage forming rubber 60lies solely at the part that projects over the second window 36 b, beingapart from the intermediate sleeve 28. With this arrangement, asdepicted in FIG. 6, the first bag-shaped portion 44 that opens to theoutside via the second window 36 a and situated at a side of opening ofan orifice passage 72 (discussed later) has the axial inside dimension:h₁ greater than the axial inside dimension: h₂ of the second bag-shapedportion 46 that opens to the outside via the second window 36 b andsituated at a side of the orifice-passage-72-formation part (h₁>h₂). Inthe present embodiment, the axial inside dimension of the first pocket42 is set substantially identical to the axial inside dimension: h₁ ofthe first bag-shaped portion 44.

Moreover, since the axial inside dimension of the first bag-shapedportion 44 is made different from the axial inside dimension of thesecond bag-shaped portion 46, the first flexible film 52 that partiallydefines the first bag-shaped portion 44 has the axial dimension greaterthan the axial dimension of the second flexible film 54 that partiallydefines the second bag-shaped portion 46. Additionally, the first andsecond flexible films 52, 54 have the thickness dimensions substantiallyequal to each other. Thus, the spring constant of the first flexiblefilm 52 in the thickness direction is smaller than the spring constantof the second flexible film 54 in the thickness direction, whereby thefirst flexible film 52 deforms more readily than the second flexiblefilm 54. It is possible to set a greater difference between the springconstants of the first and second flexible films 52, 54 by setting thethickness dimension of the first flexible film 52 smaller than that ofthe second flexible film 54.

As depicted in FIG. 5 for example, a circumferential groove 64 is formedin the passage forming rubber 60. The circumferential groove 64 is arecessed groove that opens in the outer circumferential surface of thepassage forming rubber 60 and extends for a prescribed length just shortof halfway around the circumference. As depicted in FIGS. 5 through 9,one of opposite ends of the circumferential groove 64 opens in thecircumferential end face of the first pocket 42 while the other ofopposite ends thereof opens in the circumferential end face of the firstbag-shaped portion 44, whereby the circumferential groove 64 connectsthe first pocket 42 and the first bag-shaped portion 44 with each other.Furthermore, in the present embodiment, the circumferential groove 64 isarranged such that the vicinity of the first pocket 42-side end thereofextends in the axial direction in a serpentine configuration, whereby asufficient length of the circumferential groove 64 is ensured.

Additionally, as depicted in FIGS. 5 and 6, the lengthwise medialportion of the circumferential groove 64 is formed in the section wherethe passage forming rubber 60 projects over the second window 36 b andextends in the circumferential direction while being axially above andapart from the second bag-shaped portion 46. With this arrangement, asdepicted in FIG. 9, the circumferential groove 64 is formed so as toextend in the circumferential direction axially between the axial end ofthe second bag-shaped portion 46 and the annular sealing portion 56 andstraddle the second window 36 b in the circumferential direction,ensuring a sufficient length dimension.

The passage forming rubber 60 further includes a communicating groove 66in the section located circumferentially between the second window 36 aand the second window 36 b. As depicted in FIG. 6, the communicatinggroove 66 opens in the outer circumferential surface of the passageforming rubber 60 and extends in the lower end section thereof in thecircumferential direction, with its one circumferential end connectedwith the first bag-shaped portion 44 while the other end connected withthe second bag-shaped portion 46. In the present embodiment, thecommunicating groove 66 has the widthwise dimension equivalent toapproximately ½ of the axial dimension of the passage forming rubber 60and is formed axially spaced apart from the circumferential groove 64 bya prescribed distance.

The outer tube member 14 is attached to the integrally vulcanizationmolded component 40 of this construction. Like the inner shaft member12, the outer tube member 14 is a high-rigidity member made of metal andhas a thin, large-diameter, generally round tube shape. The outer tubemember 14 is fitted externally onto the integrally vulcanization moldedcomponent 40 and then is subjected to a diameter reduction process suchas 360-degree radial compression in order to be fastened fitting withthe integrally vulcanization molded component 40. In addition, the outertube member 14 is adapted to be mounted onto the vehicle body side via abracket (not shown). Moreover, the outer tube member 14 is outwardlyfitted onto the large-diameter tubular portion 30 of the intermediatesleeve 28 via the annular sealing portions 56, whereby the annularsealing portions 56 provide a fluid-tight sealing between superposedsurfaces between the outer tube member 14 and the large-diameter tubularportion 30. In the present embodiment in particular, with the seal lips58 compressed between the outer tube member 14 and the large-diametertubular portion 30 of the intermediate sleeve 28, improved sealingcapabilities can be obtained.

By mounting the outer tube member 14 onto the integrally vulcanizationmolded component 40, the first window 34 is sealed off by the outer tubemember 14 so that the opening of the first pocket 42 is closed by theouter tube member 14. With this arrangement, there is formed a pressurereceiving chamber 68 utilizing the first pocket 42 whose wall ispartially defined by the rubber elastic body 16 and that gives rise topressure fluctuations at times of vibration input.

Additionally, the first stopper portion 22 of the stopper member 18 thatis attached to the inner shaft member 12 projects out within thepressure receiving chamber 68, with its diametrically distal end faceopposed to the outer tube member 14 with a given spacing therebetween.Meanwhile, on the opposite side of the first stopper portion 22 with theinner shaft member 12 being interposed therebetween, the second stopperportion 24 is opposed to the intermediate sleeve 28 with a given spacingtherebetween. With this arrangement, relative displacement of the innershaft member 12 and the outer tube member 14 in one diametricaldirection (the sideways direction in FIG. 2) is limited by means ofabutment of the stopper member 18 against the outer tube member 14 andthe intermediate sleeve 28.

Meanwhile, the pair of the second windows 36 a, 36 b are sealed off bythe outer tube member 14 so that the openings of the first and secondbag-shaped portions 44, 46 are both covered by the outer tube member 14.With this arrangement, there is formed an equilibrium chamber 70utilizing the first and second bag-shaped portions 44, 46 whose wall ispartially defined by the first and second flexible films 52, 54 and thatreadily permits change in volume. In the present embodiment, the openingof the communicating groove 66 is covered by the outer tube member 14,thereby forming a communicating passage through which the first andsecond bag-shaped portions 44, 46 are connected with each other. Thefirst and second bag-shaped portions 44, 46 are arranged to form the oneequilibrium chamber 70 in cooperation with each other.

A non-compressible fluid is sealed within the pressure receiving chamber68 and the equilibrium chamber 70. No particular limitation is imposedon the non-compressible fluid filling the two chambers; water, analkylene glycol, polyalkylene glycol, silicone oil, or a mixture ofthese may be favorably employed, for example. In terms of effectivelyachieving vibration damping effect based on flow action of the fluid(discussed later), it is especially preferable to use a low-viscosityfluid of 0.1 Pa·s or less as the sealed fluid. Sealing of thenon-compressible fluid within the pressure receiving chamber 68 and theequilibrium chamber 70 may be easily accomplished by carrying outassembly of the outer tube member 14 to the integrally vulcanizationmolded component 40 while these components are immersed in a tank filledwith the non-compressible fluid.

Furthermore, the outer tube member 14 closes the opening of thecircumferential groove 64 fluid-tightly thereby forming an orificepassage 72 that connects the pressure receiving chamber 68 and theequilibrium chamber 70 with each other. The orifice passage 72 isarranged such that one of opposite ends thereof opens in thecircumferential end face of the pressure receiving chamber 68 while theother of opposite ends thereof opens in the circumferential end face ofthe first bag-shaped portion 44 that defines the equilibrium chamber 70.In the present embodiment, the tuning frequency of the orifice passage72, which is adjusted based on the ratio (A/L) of passage length (L) topassage area (A) thereof, has been set to a low frequency of around 10Hz that corresponds to engine shake.

With the engine mount 10 of this construction according to the presentembodiment installed in an automobile, during input of low-frequencyvibration that corresponds to engine shake in one diametrical direction(the sideways direction in FIG. 2) between the inner shaft member 12 andthe outer tube member 14, relative pressure fluctuations will beproduced between the pressure receiving chamber 68 and the equilibriumchamber 70. Consequently, fluid flow will take place between thepressure receiving chamber 68 and the equilibrium chamber 70 through theorifice passage 72, thereby exhibiting desired vibration damping effect(high attenuating or damping action) on the basis of the resonanceaction or other flow action of the fluid.

At this point, in the engine mount 10 according to the presentembodiment, the orifice passage 72 extends out from the pressurereceiving chamber 68 towards the second bag-shaped portion 46 side,keeps on extending in the circumferential direction in the section beingaxially above and apart from the second bag-shaped portion 46, and isconnected to the first bag-shaped portion 44 situated on the oppositeside of the pressure receiving chamber 68 with the second bag-shapedportion 46 being interposed therebetween in the circumferentialdirection. Therefore, it is possible to provide a sufficient passagelength of the orifice passage 72, thereby advantageously ensuring thedegree of freedom in tuning of the orifice passage 72 to thelower-frequency side. In the present embodiment in particular, theorifice passage 72 is arranged such that the vicinity of pressurereceiving chamber 68-side end thereof extends in the axial direction ina serpentine configuration, making it possible to provide even moresufficient length dimension of the orifice passage 72.

In addition, since the orifice passage 72 is connected to the firstbag-shaped portion 44 having an expanded axial dimension in comparisonwith the second bag-shaped portion 46, connection area of the orificepassage 72 to the equilibrium chamber 70 has a sufficient volume whilethe first flexible film 52 that defines the wall of the connection areahas a sufficient area. With this arrangement, the initial pressureexerted on the equilibrium chamber 70 due to the fluid flow through theorifice passage 72 will be effectively absorbed by volume change of theequilibrium chamber 70 based on deformation of the first flexible film52. As a result, relative pressure fluctuations between the pressurereceiving chamber 68 and the equilibrium chamber 70 will be efficientlyproduced, thereby effectively achieving vibration damping effectexhibited by the fluid flow through the orifice passage 72.

Moreover, whereas the axially expanded first bag-shaped portion 44ensures a sufficient volume of the connection area in the equilibriumchamber 70 on which the initial pressure will act, the second bag-shapedportion 46 that communicates with the first bag-shaped portion 44 andintegrally defines the equilibrium chamber 70 ensures a sufficientvolume of the entire equilibrium chamber 70. Additionally, the entirearea of the flexible film that realizes volume compensation action inthe equilibrium chamber 70 is sufficiently provided by the first andsecond flexible films 52, 54. Therefore, as the amount of fluid flowthrough the orifice passage 72 increases, the entire equilibrium chamber70 exhibits volume compensation action on the pressure receiving chamber68 more effectively, thereby ensuring the amount of fluid flow throughthe orifice passage 72. As a result, excellent vibration damping effectbased on the flow action of the fluid will be more efficiently attained.

Furthermore, the opposite end portions of the orifice passage 72 thatextends in the circumferential direction open to the pressure receivingchamber 68 and the equilibrium chamber 70 in the circumferentialdirection. Accordingly, the fluid will smoothly flow in and out of thetwo chambers 68, 70, being capable of more efficiently ensuring theamount of fluid flow through the orifice passage 72. As a result,vibration damping effect based on the flow action of the fluid will bemore advantageously exhibited.

Also, in the engine mount 10, since the construction of the equilibriumchamber 70 is specifically designed so as to ensure a sufficient passagelength of the orifice passage 72, it is possible to obtain a sufficientcapacity of the pressure receiving chamber 68 while at the same timeproviding a sufficient passage length of the orifice passage 72.Therefore, a sufficient effective piston surface area of the pressurereceiving chamber 68 can be obtained, making it possible to efficientlyinduce the fluid flow through the orifice passage 72. Consequently,vibration damping effect based on the flow action of the fluid will beadvantageously exhibited, thereby improving vibration dampingcapabilities.

In addition, since the construction of the equilibrium chamber 70 isspecifically designed so as to provide the orifice passage 72 in theaxially medial portion of the engine mount 10, it is not necessary toexpand axial dimension of the engine mount 10 in order to ensure thepassage length of the orifice passage 72. This allows to achieve theengine mount 10 in a compact design that exhibits excellent vibrationdamping effect against low-frequency vibration input. Moreover, theorifice passage 72 is provided in the passage forming rubber 60 that isintegrally formed with the rubber elastic body 16 and bonded byvulcanization to the intermediate sleeve 28. With this arrangement, noorifice forming member is required as a separate element in order toform the orifice passage 72, making it possible to obtain the orificepassage 72, which extends in the axially medial portion, with a smallnumber of parts. As a result, the number of manufacturing process can bereduced, while achieving lower production cost.

Additionally, in the present embodiment, the annular sealing portions 56and the seal lips 58 that are provided at axially opposite end portionsof the intermediate sleeve 28 are able to prevent leakage ofnon-compressible fluid sealed within the interior to the outside.Moreover, the seal ribs 62 that are integrally formed with the passageforming rubber 60 are able to prevent short circuit of the fluid amongthe pressure receiving chamber 68, the equilibrium chamber 70 and theorifice passage 72. Accordingly, desired vibration damping capabilitiescan be surely maintained.

Furthermore, in the present embodiment, the passage forming rubber 60that includes the orifice passage 72 partially projects over the openingedge of the second window 36 b. In this respect, the pair of the secondwindows 36 a, 36 b are substantially identical with each other in shapeand the intermediate sleeve 28 has a symmetrical construction in thevertical direction. Therefore, when the rubber elastic body 16 is moldedby vulcanization, during setting the intermediate sleeve 28 with respectto the mold for vulcanization molding of the rubber elastic body 16, anerror in vulcanization due to setting the intermediate sleeve 28 upsidedown will be prevented, thereby avoiding occurrence of defectiveproducts.

While the present invention has been described hereinabove in terms of apreferred embodiment, this is merely exemplary, and the invention shallnot be construed as limited in any way to the specific disclosures inthe embodiment.

For example, in the preceding embodiment, the second pocket 48 isconstituted such that the first bag-shaped portion 44 and the secondbag-shaped portion 46, which opens in the outer circumferential surfacethrough mutually independent second window 36 a and second window 36 brespectively, are held in communication with each other through thecommunicating groove 66. However, it would also be acceptable for thesecond pocket, for example, to entirely open in the outercircumferential surface through one window while its substantiallyentire bottom face being defined by one flexible film. That is to say,the equilibrium chamber need not necessarily have a construction inwhich a first and second bag-shaped portions are held in communicationwith each other.

Also, while in the preceding embodiment, a part of the orifice passage72 is formed in the section of the passage forming rubber 60 thatprojects over the second window 36 b, it would also be possible forexample that one second window has a shape corresponding to the openingof the second bag-shaped portion 46 so that the pair of second windowshave different shapes from each other. With this arrangement, theorifice passage 72 will have its entire bottom portion affixed by theintermediate sleeve 28, thereby achieving a stable passage shape.

Additionally, whereas the equilibrium chamber 70 in the precedingembodiment has a stepped shape whose axial inside dimension is madelarger on the first bag-shaped portion 44 side rather than on the secondbag-shaped portion 46 side, the equilibrium chamber may alternativelyhave a tapered wall that gradually expands in the axial direction fromthe side of the orifice-passage-72-formation part towards the side ofopening of the orifice passage 72.

Moreover, while in the preceding embodiment, the orifice passage 72 isarranged such that the vicinity of pressure receiving chamber 68-sideend thereof extends in the axial direction in a serpentineconfiguration, such serpentine portion may be dispensed with, andinstead the entire orifice passage may extend in the circumferentialdirection at a certain axial level.

Further, in the preceding embodiment, the fluid-filled cylindricalvibration-damping device of construction according to the presentinvention has been shown reduced to practice in an automotive enginemount by way of example. However, the present invention may also beimplemented in fluid-filled cylindrical vibration-damping devices foruse in non-automotive applications such as train cars or motorized twowheeled vehicles, for example. Furthermore, the present invention isapplicable not just to engine mounts, but also to suspension bushings,body mounts, sub-frame mounts, differential mounts, and the like.

1. A fluid-filled cylindrical vibration-damping device comprising: aninner shaft member; a tubular intermediate sleeve disposed outward ofthe inner shaft member with a gap therebetween, and having a firstwindow and at least one second window; a rubber elastic body elasticallyconnecting the inner shaft member and the intermediate sleeve, therubber elastic body includes a first pocket and a second pocket providedat respective circumferential portions thereof while opening in an outercircumferential surface of the intermediate sleeve through the first andsecond windows of the intermediate sleeve, the rubber elastic body beingprovided with a slit so that a bottom portion of the second pocket isdefined as at least one flexible film; an outer tube member outwardlyfitted onto the intermediate sleeve in order to close an opening of thefirst pocket and define a pressure receiving chamber whose wall ispartially defined by the rubber elastic body and filled with anon-compressible fluid, and in order to close an opening of the secondpocket and define an equilibrium chamber whose wall is partially definedby the flexible film and filled with the non-compressible fluid; and anorifice passage permitting a fluid communication between the pressurereceiving chamber and the equilibrium chamber, wherein annular sealingportions are provided at axially opposite end portions between theintermediate sleeve and the outer tube member over entire circumferencesthereof, a circumferential groove is provided at so as to extend in acircumferential direction between at least one of axially opposite edgeportions of the second pocket and the annular sealing portion orportions that are opposed in an axial direction to the at least one ofaxially opposite edge portions of the second pocket, the circumferentialgroove is closed by means of the outer tube member to provide theorifice passage, one of opposite ends of the orifice passage opens tothe pressure receiving chamber in the circumferential direction, andanother of opposite ends of the orifice passage opens to the equilibriumchamber in the circumferential direction such that an axial insidedimension of the second pocket that defines the equilibrium chamber isexpanded in comparison with that of an orifice-passage-formation part ata side of opening of the orifice passage.
 2. The fluid-filledcylindrical vibration-damping device according to claim 1, wherein thesecond window of the intermediate sleeve has an axial dimensioncorresponding to that of an expanded portion of the second pocket overan entire circumferential length thereof, and a part of the secondpocket where the circumferential groove is defined is integrally formedwith the rubber elastic body, and projects axially inwardly from the oneof axially opposite edge portions of the second window.
 3. Thefluid-filled cylindrical vibration-damping device according to claim 1,wherein the second pocket includes a first bag-shaped portion and asecond bag-shaped portion, which are spaced away from each other in thecircumferential direction, wherein the at least one flexible filmcomprises a first flexible film and a second flexible film whichpartially define the first bag-shaped portion and the second bag-shapedportion respectively, wherein a communicating groove is provided forconnecting the first and second bag-shaped portions, wherein an axiallyinside dimension of the first bag-shaped portion is expanded incomparison with that of the second bag-shaped portion at least one ofaxially opposite sides to provide the orifice passage between the one ofaxially opposite edge portions of the second bag-shaped portion and theannular sealing portion in the axial direction, and wherein the otherone of the opposite ends of the orifice passage is connected to theequilibrium chamber at a portion composed of the first bag-shapedportion.
 4. The fluid-filled cylindrical vibration-damping deviceaccording to claim 3, wherein the first flexible film that partiallydefines the first bag-shaped portion has an axial dimension greater thanan axial dimension of the second flexible film that partially definesthe second bag-shaped portion while the first and second flexible filmshave thickness dimensions substantially equal to each other so that aspring constant of the first flexible film in a thickness direction issmaller than a spring constant of the second flexible film in thethickness direction.
 5. The fluid-filled cylindrical vibration-dampingdevice according to claim 4, wherein the at least one second windowcomprises a pair of second windows, and wherein the first bag-shapedportion and the second bag-shaped portion are circumferentiallyconnected with each other via the communicating groove formed in asection located between the pair of the second windows in asmall-diameter tubular portion of the intermediate sleeve so that anentire equilibrium chamber exhibits volume compensation action on thepressure receiving chamber.
 6. The fluid-filled cylindricalvibration-damping device according to claim 1, wherein the orificepassage is arranged such that a vicinity of pressure receivingchamber-side end thereof extends in the axial direction in a serpentineconfiguration.
 7. The fluid-filled cylindrical vibration-damping deviceaccording to claim 1, wherein a passage forming rubber is integrallyformed with the rubber elastic body on an outer circumferential surfaceof a small-diameter tubular portion of the intermediate sleeve, whereinthe circumferential groove is formed in the passage forming rubber, andwherein seal ribs are formed on an outer circumferential face of thepassage forming rubber and project out extending along with thecircumferential groove in the circumferential and axial direction sothat the seal ribs prevent short circuit of the non-compressible fluidamong the pressure receiving chamber, the equilibrium chamber and theorifice passage.